Non-impact printing device for electronic calculators

ABSTRACT

A non-impact printing device for electronic calculators is designed to print characters on electrosensitive paper by means of electrodes mounted on a printing head which moves across the paper for printing each line of characters and then returns to the starting point. A toothed rack in the form of a loop cooperates with a gear associated with the printing head and a driving motor for effecting the translatory motion. A platen includes a portion for line spacing comprising inclined guide tracks which cooperate with guides for advancing the paper in conjunction with the movement of the head. A further portion of the platen includes a cleaning roller over which the electrodes are swept during each cycle of movement for automatic cleaning.

Giolitti et al.

[111 3,826,915 July 30, 1974 NON-IMPACT PRINTING DEVICE FOR ELECTRONICCALCULATORS [75] lnventors: Nicolo Giolitti, lvrea; Michele Bovio,

Banchette, both of Italy [73] Assignee: lng. Co. Olivetti & Co., s.p.A.,lvrea (Torino), Italy 221 Filed: Sept. 6, 1972 21 Appl. No.: 286,801

[30] Foreign Application Priority Data Richter Zabris kie 346/74 E5/1967 Little 346/74 E 6/1969 Camras 179/1002 D Primary Examiner-JamesW. Moffitt Assistant Examiner-Jay P. Lucas Attorney, Agent, or Firm-IraJ. Schaefer [5 7 ABSTRACT A non-impact printing device for electroniccalculators is designed to print characters on electrosensitive paper bymeans of electrodes mounted .on a printing head which moves across thepaper for printing each line of characters and then returns to thestarting point. A toothed rack in the form of a loop cooperates with agear associated with the printing head and a driving motor for effectingthe translatory motion. A platen includes a portion for line spacingcomprising inclined guide tracks which cooperate with guides foradvancing the paper in conjunction with the movement of the head. Afurther portion of the platen includes a cleaning roller over which theelectrodes are swept during each cycle of movement for automaticcleaning.

17 Claims, 11 Drawing Figures PATENIEnJ'ummM SHEET 3 [IF 7PATENIEn'JuLsmeu SHEET 6 [IF 7 PATENTEBLIULSOIBH SHEET 7 OF 7 NON-IMPACTPRINTING DEVICE Eon ELECTRONIC CALCULATORS BACKGROUND OF THEINVENTION 1. Field of the Invention The present invention relates to anon-impact printing device associated with an electronic calculator orthe like for printing characters on electrosensitive paper by means ofelectrical impulses through a set of electrodes which are in contactwith the sensitive surface of the paper. The electrodes are mounted on aprinting head which 'moves transversely across the paper to print alineof characters and then returns to the starting point to repeat theprinting cycle.

2. Descriptionof the Prior Art Prior art printing systems which havemovable printing heads generally require complex and expensivemechanisms to achieve the required forward and reverse Inotion and linespacing. Such mechanisms re quire additional space and added weightmaking a com pact, lightweight electronic calculator difficult to real-Furthermore, in printing devices of the non-impact type which employelectric discharges to burn an impression onto electrosensitive paper,there is generally created a powder residue which frequently becomesdeposited onthe electrodes forming a film which interferes with properprinting. In prior art devices the removal'of'thisfilm was eitheraccomplishedby complex auxiliary devices or else,]manually, thusrequiring the machine to be taken out-of service regularly for cleaningpurposes. I

OBJECTS AND SUMMARY OF THE INVENTION The disadvantages of known devicesare overcome in the inventive printing device for electronic calculatorsby providing translating means for the printing head for shifting thelatter in one direction across the printing paper to print a line ofcharacters and back to'the rest position. The translating means includesa toothed rack in the form of a loop which is engaged by a gearassociated with the printinghead and a driving motor. A platen forsupporting the printing paper has also associated with it a line spacingmechanism for advancing the paper in conjunction with the movement ofthe printing head.

Means for cleaning the electrodes automatically during each tr'anslatorycycle of movement of the printing head is'also provided. I

These and other features of the invention will become apparent from thefollowing description of a preferred embodiment and accompanyingdrawings.

I BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side view in section ofthe printing device for electronic calculators according to theinvention;

FIG. 2 is a, planlview of the printing head;

FIG. 3 is a sectional. view. taken along line III-III of 1 FIG. 8 is afront view of a detail of FIG. 5, partially in section; FIG. 9 is aschematic of a portion of the electronic control system for the printingdevice; I

FIG. 10 is a block diagram showing the electronic control system for theprinting device;

FIG. 11 is a partial sectional view of an alternative method of couplingthe printing head for movement.

DETAILED DESCRIPTION OF THE INVENTION The printing apparatus accordingto the invention is intended for use in electronic business calculatorswhich print characters on electrosensitive material, such as metallizedpaper. I Referring now to FIG. 1, the printing apparatus includes aprinting head 10 mountedin proximity to a platen 11 along which the headis movably positioned for printing characters on an electrosensitivepaper tape 12 which is threaded between the head 10 and the platen ll.

As shown in FIG. 2, the printing head 10 includes a body 13 preferablyformed of plastic insulatingmaterial and having a portion 14 extendingtherefrom (FIG. 3) which is slightly curved on its underside forcontacting the surface of the paper tape 12 which is to be printed. Thecurved underside portion of extension 14 is formed with a substantiallyW-shaped channel-18 (FIG. 4) in whichanumber ofvmetallicelectrodes 15are aligned parallel to the longitudinal axis of the paper strip, eachof the electrodes being of a length suitable for contacting the stripand platen. Each of the electrodes 15.is integral with a conductor 16,made of ma- I terial such as tungsten wire, or the like, which iselectri-.

cally connected to the control circuit by means of 'acorrespondingconductivetrack 17 which forms part of a printed circuitcontrol assembly to be hereinafter described. Each of the conductors 16is equally spaced from eachother and is shaped in the form of a rightangle 19 at the point of contact with conductive track 17 and issupported at said point away fromthe body 13 of printing head 10. Inthis manner, each conductor 16 makes resilient contactwith itscorresponding track 17 thus assuring good electrical contact between theelements as the printing head Ill-moves for-effecting printing.

In order to maintain the conductors 16 in alignment with thecorresponding track 17 while permitting resilare aligned with therightangle portions 19 of conductors 16 in order to make electrical contactwith corresponding conductors 23, 24 of the printed circuit whosefunction will be hereinafter described.

On the side opposite the extending portion 14, the body 13 is providedwith a bore 25 (FIG. 3) for permitting the head 10 to pivot and slidealong a shaft 26 (FIG. 5) supported between two frames 27, 28 of themachine chassis 29. The body 13, in addition, includes a secondextension 30 (FIG. 3) in the form of an I.

for engaging the mechanism for advancing the printing head along theplaten 1'1.

The advancing mechanism for theprinting head 10 comprises a carriage 31(FIG. 1); preferably of plastic material, having 'a rectangularprismoidal shape, disposed parallel to and beneath shaft 26 in acorrespondis provided a second channel 40 which serves as a guidetrackin whichis inserted the extension of a pin 41. A toothed wheel or gear42 is mounted on pin 41 for insertion into channel 34 and engagementwith the row of teeth 39 thereby forming a rack and pinion arrangement.The extension of pin 41 keeps the gear 42 at the proper distance fromthe row 39 to maintain constant engagement between the teeth of saidgear and row. The gear42 is integrally'formed with a second toothedwheel or gear 43 having a larger diameter. Gears 42, 43 and pin 41 aresecured to the larger end of a plate 44 (FIGS. 5, 6) having asubstantially oval shape the smaller end of which is pivotable about adrive shaft 45. The gear 43 meshes with driving gear 47 having'a shaft45 which is rotated by an electric motor 46. Upon excitation of themotor 46, shaft 45 and driving gear 47 cause the gears 42 and 43 torotate. Gear 42 meshing with teeth 39 constrains the carriage 31 to movealong the channel 34. During this movement, whenever the gear 42 reachesone of the 'curves 37, 38 of the toothed rack 39, the plate 44, beingfixed to shaft 41 and-pivotable about the motor shaft 45, function as acrank arm to constrain gear 42 to follow the channel 34 around its'curvedportion and then moving along theopposite straight track. Thusthe carriage 31 is made to undergo a transfer in its direction ofmotion.

The edge of side 32 also includes a rectangular cutaway portion 49(FIGS. 1, 6) in which a finger .30 of printing head 10 is insertedinorder to couple the head 10 to the movement of carriage 31. Theback-and-forth translatory motion of the carriage 31 governs theadvancement of the printing head 10, along shaft 26 be tween the twofixed end points of travel.

The formation of cutaway portion 49 permits head 10 to move loosely in avertical direction to a limited degree thus allowing resilient contactbetween the paper 12 and electrodes 16 sliding along the printed circuit17, the electrodes beingmounted with certain initial pressure withrespect to the printed circuit board.

To prevent the carriage 31 from sliding out of channel 32 or beingmisaligned during its back-and-forth movement a cover panel 50 serves asa closure member. Panel 50 includes a rectangular slit-51 (FIG. 6) for.allowing finger 30 of the head 10 to be inserted into cutaway 49 ofcarriage 31 and an additional cutout 52 for permitting the plate 44 andgear 42 to shift position whenever the curved portions of the rack 39are reached. I V

The back-and-forth movement of carriage 31 is utilized to implement theline spacing function of the apparatus. Carriage 31 includes a curvedsurface 55 (FIGS. 7, 8). located opposite its surface 33, on which areformed three substantially rectangular and parallel ribs 56, 57, 58.Thethree ribs, accordingly, define two guide tracks '59, 60., Track 59includes a first portion which is inclined with respect to thelongitudinal axis of surface, 55 and continues with a portionwhichparallels said axis while track 60 is parallel to. the firstportion of track 59. The two tracks 59, 60 engage two protrusions 61, 62(FIG. 7) of an arm 63 secured to a disk 64 forming part of theline-spacing assembly 65 pivotable about the axis of rotation of theplaten 31. Arm 63 includes a toothed crown section 66 (FIG. 8) extendingThe internal bore 76 of hub engages a shaft 77 which is the cylindricalextension of the plate 11. Shaft 77 is provided with athreaded bore 78'at its end into which a screw 80, passing through hole 79 in crown 70,joins the latter to the platen 11. The crown .70 is further joined tothe platen 11 by two diametrically opposite studs 81, 82, located at theend of hub 75, which are inserted in twocorresponding apertures 83,84 ofthe cylindrical extremity of platen 11. The crown 70 is kept separatedfrom the chassis 29 by means of circumferential step 86 around hub 75. i

The previously-mentioned, line spacing assembly includes a cross-shapedmember 87 having an elongated arm 88 (FIG. 7). The center portion ofmember 87 is bored to permit insertion of shaft 75. Furthermore, member87 includes grooves 89, 90, 91 which nate, respectively, with lugs 67,68, 69 of the line-spacing assembly for securing the member to theassembly.

Member 87 is maintained in position by means of the arm 88 whichresiliently contacts the side 74 of chassis 29 (FIG. 5), thus constantlyurging crown section 66 of line spacing assembly 65 against the toothedcrown '70.

Accordingly, whenever the carriage 31 is moved in response to actuationof electric motor 46, the tracks 59, 60 cause the line spacing assemblyto shift about the collinear axes of platen 11 and crown 70. During thefirst phase of the shifting motion, the teeth of crown section 66 (FIG.8) act against those of crown 70 turning the latter through a certainangle together with the platen 11 to which crown 70 is joined. Duringthe next phase the teeth of crown section 66 slip across the teeth ofcrown 70 and mesh with the nextadjacent tooth, thus undergoing a ratchettype of movement as a result of the spring action of arm 88 urging thetoothed members together. In this phase of the line shifting movement,the platen 11 remains motionless while the line spacing assembly 65 isreadied for a successive shifting movement of crown 70. I

The platen 1 1 (FIG. 5) includes a shaft, preferably of plastic, havinga central portion 95 on which a layer of soft rubber 99 is deposited forsupporting the paper tape 12 to be printed. The extreme ends of platen11 comprise two equal cylinders 77, 97 which are journaled,respectively, in seat 73 of side 74 and ,seat 98 of side 28 of thechassis 29.

In addition, platen 11 incorporates a cylindrical portion 85 locatedbetweenplaten sections 77 and 96 which is seated in a cylindricaljournal 1011 joined to side 79.of chassis 29. The axis of journal 100 isslightly raised relative to the axis of platen '11, having, however, thesame distance from the axis. of shaft 26 as the latter bears oftheplaten axis.

Journal 100, accordingly, is off center with respect to the axisofplaten 11 while remaining coaxial relative to the curved undersideportion of extension 14 of the printing head 10.

A cylindricalcleaning roller 101 mounted around journal 100 is adaptedto-clean the ends 15 of electrodes 16. The roller 101 has a portionwhich fits around cylindrical platen. portion 85, extending into aannular rim 102 and is further provided with a knurled external surface.Rim 102 includes a projection 103 which wedges with a correspondingopening 104 in section 96 of platen 11 for rotation therewith.

The internal bore of cleaning roller 101 which turns around journal. 100is eccentric with respect to its external knurled surface. Thus,whenever platen 11 rotates by the line spacing apparatus the externalsurface of cleaning roller 101 varies in height relative to the axis ofthe platen. I

Mounted about rim 102 of roller 101 is an elevating ring 110 having anedge 111. Ring 110 has a'lug 113 suitably inserted into chassis 29 forpreventing rotation of said ring as well as a tapered finger 112extending parallel to platen 11. Finger 112 extends along and is slighlydisplaced from the surface of platen 11 and extends slightly beyond the.edge of the paper tape 12 against the platen surface. A curved undersidematches the curved surface of the platen 11 (FIG. 1).

The purpose of elevating ring 110 is to protect the edges of the papertape 12 as the printing head moves away from the cleaning roller 101.The ring 110 and in particular the finger 112 which is slightlytapereddown towards the platencause the head 10 to become lifted as to movetowards cylinder 101 and as it returns the head.l0 is guided beyond theedge of tape 12 and down towards the platen, thus avoiding tearing ormisaligning-the paper through contact with the edge. Sliding contactbetween the finger 112 and the extension 14of head 10 is facilitated bythe complimentary profile of the respective engaging surfaces. Finger112 also serves as a paper tape 12 guide for keeping the tape againstthe platen 11 as well as maintaining the tape edge in proper registry;

The knurled external surface of cleaning roller 101 is level with theexternal end of finger 112 due to the eccentricity of journal 100relative to platen 11. The printing head 10 has an extreme limit oftravel of the leftmost point of cleaning roller 101 and thus as the leadtravels back and forth the ends of electrodes 16 contact the knurledsurface of said roller. This action serves to liberate the electrodes ofpowder (which would cause an insulating film) which accumulates as thehead sweeps across the paper during printing. The shape of the notchedchannel 18 also aids in preventing the formation of an insulating filmby forming a chamber fordepositing the powder which would otherwiseaccumulate on the electrodes.

The eccentricity of cleaning roller 101 assures the cleaning ofelectrodes 15 regardless of any errors in mounting or manufacturing theparts; particularly between shaft 26 on which the printing head 10pivots which are arranged in a row. Thus, as platen 11 makes a completeturn the row of electrodes 15 is swept across the surface of roller 101and the electrode cleaning process is achieved and proper printing onthe electrosensitive paper is assured.

The paper tape 12 is fed by means of platen 11 on which it rests bymeans of two paper pressure rollers 115, 116 (FIG. 5) mounted on a shaft117 which rotates between two cutouts 118, 119 of chassis 29. Therollers 1 15, 116 are separated in the center part of shaft 117 to allowthe insertion of the forked end of an arm 118 (FIG. 1). The opposite endof arm 118 includes a semicircular notch 119 for engaging one end of abar 120 (FIG. 5). The other end of bar 120 is engaged by the end of alever 122 which includes a finger 123 and a tab 124. Tab 124 engages oneend of a metal-spring I ing the pressure rollers 115, 116 to pressagainst platen Rollers 115, 116 may be lifted away from the surface ofplaten 11, in case it should be necessary; for instance, in order toreplace the roll of paper tape 12, by raising the cover plate 126 whichpivots on shaft 127. The cover plate 126 includes a leg 129 which, whenthe cover is raised, cooperates with finger 123 of lever 122 causing thelatter to rotate clockwise thus also shifting bar and rollers 115, 116away from the platen 11.

The rollers 115, 116, arm 118, bar 120, lever 122 and spring comprise,in addition, the electrical return path for the printing circuit. Theelectrical signals which are fed through electrodes 16 and points 15 areconducted across the metallized layer of the electrosensitive paper 12and thence to rollers 115, 116, eventually reaching spring 125 and theprinted circuit at point 130. It can be seen, therefore, that spring 125has both a mechanical and electrical function in the describedembodiment.

The printing operation takes place when the appropriate keys on thekeyboard (not shown) are depressed. This causes the electrical motor 46(FIG. 7) to beactuated, which through gears 42, 43, 47 causes thecarriage 31 and coupled printing head 10 to shift. The head 10 which islocated at its rest position at the outer edge of the cleaning roller101 shifts toward its other extreme position, located at the right edgeof the paper tape 12 and back again.

During this cylical shift, the two blades of an electrical contact wiper21, joined to head 10, sweep along corresponding parallel conductivetracks 23, 24' of the printed circuit board 17.

Track 23 has a portion 141 (FIG. 9) which is interrupted and, therefore,nonconductive and serves to initiate an electrical impulse for use bythe electronic control system as hereinafter described. The interruptedportion 141 is located just prior to the point on the paper tape 12 atwhich a line of printing is to commence. In the rest position ofprinting head 10 the wiper 21 isbridged across the common conductivetrack 24 and the first portion 23 of the interrupted track23.-

As printing head 10 moves across the paper tape 12 the wiper 21 movescorrespondingly, first contacting track section 23' then the interruptedportion 141 and finally track section 23". When wiper 21 is at portion141 electrical continuity between tracks 23 and 24 is interrupted. Thiselectrical interruption may be utilized to signal the position of theprinting head.l as being at theprecise beginning of a printing line tothe trigger 202 (FIG. of the electronic control system and thus causesthe printing of the characters to commence.

After printing a line of characters, the head 10 returns to the startingposition and wiper 21 sweeps from section 23" to section 23. The makingof electrical contact with section 23', after the interruption 141,

serves to signal to the electronic control system that the motor 46should be turned off. Upon turning off motor 46 the printing head 10returns to its rest position, the short distance being reached by theinertia of the head 10 as it moves back. Head 10 remains in the restposition .until a new cycle of operation is initiated.

Although the electronic system for governing printing forms no part ofthis invention, a brief description thereof will be given. The system isparticularly adapted for. printing characters in the well-known formatof a 5X7 matrix consisting of five columns each being printedsequentially, each column being comprised of seven row elements. Thematrix is generated by means of an integrated circuit read only memory Acolumn timing network 205 is provided for governing the sequentialprinting of each of the columns containing row elements of the characterto be printed. The timing network 205 is connected to each of the ANDgates 209 and causes each of the five AND gatesto be turned onsequentially, that is with a predeter- (ROM) 200 which is pre-programmedfor generating alphanumerical characters when the ROM is fed with asuitable input code. Such memory units are presently available off theself and, consequently, their structure and operation, being wellunderstood, need not be detailed herein.

Coded characters which represent the characters to be printed are fed bythe output registers of the logic unit of the calculator (not' shown)through an adapter network 201 (FIG.10) for converting the logicaloutput of the logicunit to logic compatible with MOS circuitry (e.g.DTL-TTL logic to MOS logic). The characters fed from the logic unit mayconsist of a' six digit code, each digit being fed through a separatechannel through individual logic adapter circuits included in network201 and then into the ROM 200. The ROM 200 decodes and transforms thecoded digits into matrix form representative of the row portions of thecharacter to be printed having a 5X7 format.

The ROM 200 is fed with another set of channels which are intended tocontrol the sequential printing of the columns of the 5X7 character. Asignal is derived from the position of the carriage 31 during itsbackand-forth movement to indicate that the carriage has reached thepoint where printing of the characters is to begin. This signal is fedinto a trigger circuit 202 which initiates therunning of an oscillatoror clock 203. The output of clock 203 is fed to a seven bit shiftregister 204 in which a stored bit is shifted one stage at a timethrough each of its seven positions in a well-known manner.Outputchannels are connected to five adjacent positions of register 204leaving two successive positions floating," for a purpose to bedescribed.

The five output channels are each connected to one input of anassociated AND gate 209.

head 10 for proper printing of the characters.

The two adjacent floating positions of the serial register 204 serve thepurpose of providing twocolumns of spacing between successive charactersfor insuring legibility by not sending any columnar printing informationto the ROM during the time that the printing head moves through adistance of two columnar spaces. The outputs of the AND gates 209 arefed through a logic interface 206 comprised of individuallogical'adaptors associated with each channel for compatibility withMOS-type logic.

Upon the arrival of the bit stored in serial register 204 at the finalposition it is then fed out after a cycle of seven positions to atrigger network 207 connected to clock 203 which is haltedupon receivingthe trigger pulse. l

The output of the ROM 200 comprises seven output leads corresponding tothe number of rows of the matrix character printed. Each lead will beelectrically activated during the time interval when the correspondingrow is-to be printed as generated by the ROM 200 in accordance with thedata input of character information from the logic unit and timecontrolfrom the shift register 204. A seven channel logic interface 208 adaptsthe MOS-type logic of the ROM 200 to the logic required by the electrodedriving network 210.

- The electrode driving network 210 includes an individual driverassociated with each channel and thus with each electrode and serves toraise the power of the signals to an appropriate level as required bythe paper characteristics for proper printing. 4

Referring now to FIG. 11, there is shown an alternative method forcoupling the movement of carriage 31 to the body 13 of printing head 10as well as to regulate the tension of the electrodes 16 as they slidealong the conductive tracks of the printed circuit control assembly l7.

Carriage 31 is retained in channel 32 of chassis 29 by a panel 50 and isprovided with an insert 304 on its external side which insert'304accomodates a threaded bolt 303 extending through an opening in panel50. One end of a resilient leaf 301 is positioned over the external endof bolt 303 on which is threaded a regulating nut 302. The other end oflead 302 is fixedly attached to printing head body 13. 1

The free end of leaf 301 is normally biased in a clockwise direction, asviewed in FIG. 11, and thuswhen pressing against nut 302 causes theprinting head body 13 to become biasel in a counterclockwise directionabout shaft 26. Since electrodes 16 are urged against tracks by theirown resilient action, by adjustment of the nut 302 the tension load onelectrodes 16 may be regulated.

- It is to be understood that the inventive printing device forelectronic-calculators herein described may be changed or modifiedwithout departing from the scope of the invention which is-totbemeasured solely from the appended claims.

What is claimed is:

1 Non-impact printing apparatus for printing lines of information on arecord medium, including a platen for carrying said record medium, acarriage, motive means for moving said carriage with respect to saidplaten, and comprising: i

a loop shaped rack recessed in one side of said carriage, said loopshapedrack including two rectilinear portions parallel to said platenand curved portions joining said rectilinear portions;

a pinion driven by said motive means;

and means for holding said pinion in continuous engagememt with saidloop shaped rack for producing-reciprocal motion of said carriage acrossthe platen, a printing head being carried by said carriage, in contactwith the record medium carried by said platen. g 2. Non-impact'printingapparatus as set forth in claim 1, wherein said holding means comprise aguiding member carried by said pinion and guide elements integral withsaid carriage and substantially parallel to said curved portions tocooperate with said guiding member.

3. Non-impact printing apparatus as set forth in claim 2 wherein saidguiding member includes a projection axially projecting from saidpinion,and said guide elements include a groove further recessed in saidcarriage and having edges parallelto said loop shaped rack.

4. Non-impact printing apparatus as set forth in claim 1 wherein saidmotive meanscomprise a driving shaft, said shaft being axially fixed,transmission means for couplingthe rotation of said shaft to saidpinion,and means pivotal with respect to said driving shaft for positioningsaid pinion on a predetermined radial distance from said driving shaftallowing said pinion to follow said curved portions of said loop shapedrack.

5. Non-impact printing apparatus as set forth in claim 1, furthercomprising:

guide track means included in said movable carriage andinclined withrespect to the path of translatory motion of said carriage;

an arm member rotatable mounted coaxial with respect to said platen andadjacent thereto, said arm member having guide element means cooperatingwith said guide track means'for rotating said arm member as aconsequence of the movement of said guide track means as said carriagemoves; and unidirectional coupling means for transmitting the rotationof said arm member to a unidirectional rotation of said platen for linespacing of the record medium carried by said platen.

6. Printing apparatus for electronic calculators for printing characterson a recording medium of the electrosensitive type, comprising:

printing head means for supporting a plurality of electrodes forcontacting the surface of said recording medium;

support means for supporting the recording medium,

a carriage carrying said printing head and movable transversely of saidsupport means;

driving means for imparting relative motion between said printingheadmeans and said support means to effect printing of characters;

said driving means compising motor means for generating motion,converting means coupled for movement with said printing head'means forconverting the motion of said motor means to translator motion of saidcarriage transversely of said support means, and guide means forcooperating with said support means for causing said support means tomove said recording medium in response to said translator motion;

said converting means comprising toothed members of said motor meansincluding first and second toothed wheels secured to a shaft, saidsecond wheel being rotatably driven by said motor means;

a firstchannel provided on one side of said carriage, said channelextending parallel to the direction of motion of said carriage andincluding parallel straight portions joined by curved portions at the Iend thereof, said straight and curved portions being provided with acontinuous row of teeth for being engaged by said first toothed wheel,and

a second channel further provided on said carriage and extendingparallel to said first channel;

said shaft extending into said second channel for guiding thetranslatory motion of said toothed members and said carriage duringengagement of the straight portions of said row of teeth by said firstwheel, and for reversing the direction of said translatory motion duringengagement of the curved portions of said row of teeth by said firstwheel; and

said shaft being held at a fixed distance from said toothed members ofsaid motor means, whereby said first wheel is maintained inconstant-engagement with said row of teeth at each portion thereof.

7. Non-impact printing apparatus for electronic calculators for printingcharacters on a recording medium of the electrosensitive type,comprising:

printing head means for supporting a plurality of electrodes having endscontacting the surface of said recording medium;

a cylindrical platen for supporting the recording medium, said ends ofsaid electrodes being disposed along a cylindrical surface correspondingto the cylindrical surface of said platen;

a cylindrical cleaning roller contiguous to said platen and having anaxis parallel with said platen and a diameter substantially equal tothat of said platen, said cleaning roller having a cleaning surface forcleaning said ends of said electrodes when in sliding contact therewith;

means for reciprocally transporting said printing head means across saidplaten and said cleaning roller for printing lines of characters on saidrecording medium and for cleaning said ends of said electrodes;

driving means for rotating said platen to space said recording medium;and I means for joining said cleaning roller to said platen for movementof said roller about said parallel axis.

8. Non-impact printing apparatus as set forth in claim 7 wherein saidroller surface is eccentric with respect to said parallel axis, so thatthe rotation of said roller, following saidspace; rotation of saidplatencauses the distance of said cleaning surface to-said parallel axis tovary,- whereby contact between said cleaning surface and each of saidelectrodes is promoted. v .9. Non-impact printing apparatus as set forthin claim 7 wherein said platen is provided with protecting means forprotecting an edge of said recording medium adjacent to said cleaningroller during said stroke of said printing head means external to saidrecording medium.

l0. Non-impact printing apparatus as set forth in claim 9, wherein saidprotecting means comprises a fixed ring mounted about said platen, saidring having an extension for covering one edge of said recordingmedium,'and said extension serving to lift said printing head meansduring movement thereof.

11. Non-impact printing apparatus as set forth in claim 7, wherein saidcleaning roller surface is knurled.

12. Non-impact printing apparatus for electronic calculators as setforth in claim 7, wherein said platen is rotatable about a fixed axisand said printing-head is slidably pivoted about a pivoting axisparallel to said platen, said cleaning roller being supported offsetwith said fixed axis of said platen but coaxial with the cylindricalsurface of said electrode ends.

13. Printing apparatus as set forth in claim 7, wherein a part of saidwriting electrodes contiguous to said writing ends is retained in acavity of said printing head support adapted to collect particles formedas result of the action of said electrodes of said record medium.

14. Non-impact printing apparatus for electronic calculators forprinting characters on an electrosensitive recording medium, comprising:

a platen supporting said recording medium;

a plurality of electrodes having writing ends contacting the surface ofsaid medium for printing;

a printing head support rigidly retaining portions of said electrodesajacent to said writing ends, said writing electrodes including,opposite to said rig- 12 idly retained portions, resilient portionsprojecting from said printing head support; a shifting means forshiftingsaidprinting'h ead support transversely to said medium;

an external control circuit for feeding said electrodes; and aconductive tracks of a circuit support connected to said control circuitand adjacently mounted to said printing head support, said tracks beingparallel to each other and to said platen, for slidably and resilientlycontacting said resilient portions of said elec- I trodes during theshifting of said printing head. 15. Printing apparatus as set forth inclaim 14, wherein said'shifting means include a carriage, said printinghead support being connected to said shifting means by means of aresilient member having one end v integral with saidprinting headsupport and theother end engaging with a member adjustably fixed to saidcarriage. I t

16. Printing apparatus as set forth in claim 14, wherein said resilientportions of said writing electrodes are shaped in form of substantiallyright angles, the ends of said electrodes opposite to said writing endsbeing guided on corresponding holes of said printing head support.

17. Printing apparatus as set forth in claim 14, wherein said externalcontrol circuit further includes an actuating circuit for actuating saidshifting means for the starting of printing of characters and saidcircuit support includes two further conductive tracks con nected tosaid actuating circuit, said printing head support including tworesilient contact shoes supported at one end by said printing headsupport ahdcooperating with the other end with said two furtherconductive tracks, one of said two further tracks having an interruptedportion substantially near the beginning of the shifting movement ofsaid printing head support to constitute a switching'point to stop theactuation of said shifting means.

1. Non-inpact printing apparatus for printing lines of information on arecord medium, including a platen for carrying said record medium, acarriage, motive means for moving said carriage with respect to saidplaten, and comprising: a loop shaped rack recessed in one side of saidcarriage, said loop shaped rack including two rectilinear portionsparallel to said platen and curved portions joining said rectilinearportions; a pinion driven by said motive means; and means for holdingsaid pinion in continuous engagememt with said loop shaped rack forproducing reciprocal motion of said carriage across the platen, aprinting head being carried by said carriage, in contact with the recordmedium carried by said platen.
 2. Non-impact printing apparatus as setforth in claim 1, wherein said holding means comprise a guiding membercarried by said pinion and guide elements integral with said carriageand substantially parallel to said curved portions to cooperate withsaid guiding member.
 3. Non-impact printing apparatus as set forth inclaim 2 wherein said guiding member includes a projection axiallyprojecting from said pinion, and said guide elements include a groovefurther recessed in said carriage and having edges parallel to said loopshaped rack.
 4. Non-impact printing apparatus as set forth in claim 1wherein said motive means comprise a driving shaft, said shaft beingaxially fixed, transmission means for coupling the rotation of saidshaft to said pinion, and means pivotal with respect to said drivingshaft for positioning said pinion on a predetermined radial distancefrom said driving shaft allowing said pinion to follow said curvedportions of said loop shaped rack.
 5. Non-impact printing apparatus asset forth in claim 1, further comprising: guide track means included insaid movable carriage and inclined with respect to the path oftranslatory motion of said carriage; an arm member rotatable mountedcoaxial with respect to said platen and adjacent thereto, said armmember having guide element means cooperating with said guide trackmeans for rotating said arm member as a consequence of the movement ofsaid guide track means as said carriage moves; and unidirectionalcoupling means for transmitting the rotation of said arm member to aunidirectional rotation of said platen for line spacing of the recordmedium carried by said platen.
 6. Printing apparatus for electroniccalculators for printing characters on a recording medium of theelectrosensitive type, comprising: printing head means for supporting aplurality of electrodes for contacting the surface of said recordingmedium; support means for supporting the recording medium, a carriagecarrying said printing head and movable transversely of said supportmeans; driving means for imparting relative motion between said printinghead means and said support means to effect printing of characters; saiddriving means compising motor means for generating motion, convertingmeans coupled for movement with said printing head means for convertingthe motion of said motor means to translator motion of said carriagetransversely of said support means, and guide means for cooperating withsaid support means for causing said support means to move said recordingmedium in resPonse to said translator motion; said converting meanscomprising toothed members of said motor means including first andsecond toothed wheels secured to a shaft, said second wheel beingrotatably driven by said motor means; a first channel provided on oneside of said carriage, said channel extending parallel to the directionof motion of said carriage and including parallel straight portionsjoined by curved portions at the end thereof, said straight and curvedportions being provided with a continuous row of teeth for being engagedby said first toothed wheel, and a second channel further provided onsaid carriage and extending parallel to said first channel; said shaftextending into said second channel for guiding the translatory motion ofsaid toothed members and said carriage during engagement of the straightportions of said row of teeth by said first wheel, and for reversing thedirection of said translatory motion during engagement of the curvedportions of said row of teeth by said first wheel; and said shaft beingheld at a fixed distance from said toothed members of said motor means,whereby said first wheel is maintained in constant engagement with saidrow of teeth at each portion thereof.
 7. Non-impact printing apparatusfor electronic calculators for printing characters on a recording mediumof the electrosensitive type, comprising: printing head means forsupporting a plurality of electrodes having ends contacting the surfaceof said recording medium; a cylindrical platen for supporting therecording medium, said ends of said electrodes being disposed along acylindrical surface corresponding to the cylindrical surface of saidplaten; a cylindrical cleaning roller contiguous to said platen andhaving an axis parallel with said platen and a diameter substantiallyequal to that of said platen, said cleaning roller having a cleaningsurface for cleaning said ends of said electrodes when in slidingcontact therewith; means for reciprocally transporting said printinghead means across said platen and said cleaning roller for printinglines of characters on said recording medium and for cleaning said endsof said electrodes; driving means for rotating said platen to space saidrecording medium; and means for joining said cleaning roller to saidplaten for movement of said roller about said parallel axis. 8.Non-impact printing apparatus as set forth in claim 7 wherein saidroller surface is eccentric with respect to said parallel axis, so thatthe rotation of said roller, following said space rotation of saidplaten causes the distance of said cleaning surface to said parallelaxis to vary, whereby contact between said cleaning surface and each ofsaid electrodes is promoted.
 9. Non-impact printing apparatus as setforth in claim 7 wherein said platen is provided with protecting meansfor protecting an edge of said recording medium adjacent to saidcleaning roller during said stroke of said printing head means externalto said recording medium.
 10. Non-impact printing apparatus as set forthin claim 9, wherein said protecting means comprises a fixed ring mountedabout said platen, said ring having an extension for covering one edgeof said recording medium, and said extension serving to lift saidprinting head means during movement thereof.
 11. Non-impact printingapparatus as set forth in claim 7, wherein said cleaning roller surfaceis knurled.
 12. Non-impact printing apparatus for electronic calculatorsas set forth in claim 7, wherein said platen is rotatable about a fixedaxis and said printing head is slidably pivoted about a pivoting axisparallel to said platen, said cleaning roller being supported offsetwith said fixed axis of said platen but coaxial with the cylindricalsurface of said electrode ends.
 13. Printing apparatus as set forth inclaim 7, wherein a part of said writing electrodes contiguous to saidwriting ends is retained in a cavity of said printing head suppOrtadapted to collect particles formed as result of the action of saidelectrodes of said record medium.
 14. Non-impact printing apparatus forelectronic calculators for printing characters on an electrosensitiverecording medium, comprising: a platen supporting said recording medium;a plurality of electrodes having writing ends contacting the surface ofsaid medium for printing; a printing head support rigidly retainingportions of said electrodes ajacent to said writing ends, said writingelectrodes including, opposite to said rigidly retained portions,resilient portions projecting from said printing head support; shiftingmeans for shifting said printing head support transversely to saidmedium; an external control circuit for feeding said electrodes; andconductive tracks of a circuit support connected to said control circuitand adjacently mounted to said printing head support, said tracks beingparallel to each other and to said platen, for slidably and resilientlycontacting said resilient portions of said electrodes during theshifting of said printing head.
 15. Printing apparatus as set forth inclaim 14, wherein said shifting means include a carriage, said printinghead support being connected to said shifting means by means of aresilient member having one end integral with said printing head supportand the other end engaging with a member adjustably fixed to saidcarriage.
 16. Printing apparatus as set forth in claim 14, wherein saidresilient portions of said writing electrodes are shaped in form ofsubstantially right angles, the ends of said electrodes opposite to saidwriting ends being guided on corresponding holes of said printing headsupport.
 17. Printing apparatus as set forth in claim 14, wherein saidexternal control circuit further includes an actuating circuit foractuating said shifting means for the starting of printing of charactersand said circuit support includes two further conductive tracksconnected to said actuating circuit, said printing head supportincluding two resilient contact shoes supported at one end by saidprinting head support and cooperating with the other end with said twofurther conductive tracks, one of said two further tracks having aninterrupted portion substantially near the beginning of the shiftingmovement of said printing head support to constitute a switching pointto stop the actuation of said shifting means.